How Long Does Diesel Fuel Last In Storage?

One of the costs that has to be factored in when dealing with any sort of transportation work is fuel. The large fluctuations in diesel fuel prices – especially in recent times – many choose to buy in bulk, storing the fuel they need for their trucks on-site, yet even this has a cost attached to it. There are costs associated with leaving fuel unused, but more importantly, there are the issues of fuel degradation.

How Long Does Diesel Fuel Last?

The problem here is twofold. First, diesel fuel is carbon-based petrochemical and thus starts the process of oxidization as soon as it departs the refinery, with the sediments and gums that clog fuel beginning to form. So how long does diesel fuel last? Well, without diesel fuel additives, diesel can go bad in as little as 30 days before this oxidization process becomes unwieldy, creating deposits that can damage fuel injectors, fuel lines, and other system components which will hurt fuel economy and performance.

Water is a major issue in diesel fuel for a couple of reasons. One is new blends of diesel often contain some biodiesel which inherently has more water in it. This water, if not separated from the fuel, can make it through the system and into the fuel injectors. Newer common rail fuel systems run at pressures up to (40,000) PSI. If even a tiny droplet of water makes it through one of the new high-pressure systems to the fuel injector it can blow the tip-off, which is an expensive repair. Just like oxidization, this slime will clog the fuel and impart long-term damage.

You can minimize your water issue by keeping your tank full which minimizes the amount of condensation space in the tank, thus reducing the amount of water. Secondly, you can use diesel fuel treatments which demulsify or separate water from the fuel. Almost all diesel engines are equipped with a Fuel Water Separator (FWS) filter. Demulsification enhances the performance of the (FWS). All OEM manufacturers recommend that you demulsify water from diesel fuel so it can safely be removed and not damage your engine. Standard good fuel maintenance practices need to be followed for fuel storage tanks. Those practices involve periodic removal of water that has gathered at the bottom of the tank. Water is heavier than fuel and free water will drop to the bottom which is a better place for it than in your fuel system. Maintenance doses of a dual phased (works in water and fuel phases) biocide twice a year are also recommended to prevent microbial growth.

For oxidization, you’ll want to invest in a diesel fuel stabilizer; Diesel fuel is very different from gasoline and needs specific technology to work properly. For best performance do not use fuel additives that claim to work in both gas and diesel.

Fuel stabilizers called antioxidants are necessary for any storage longer than 30 days and should be used while the fuel is still fresh. While it’s necessary for diesel storage, it’s wise to use it in any vehicle that hasn’t been used with some frequency.

What Does the Fuel Industry Say?

So how long does diesel fuel last under these conditions? Exxon states that “diesel fuel can be stored 6 months to 1 year without significant fuel degradation if you keep it clean, cool and dry.” Chevron adds that diesel fuel can be stored longer than a year under certain conditions:

First, the fuel was purchased clean and dry from a reliable supplier.

Second, appropriate fuel quality and stability was achieved through the use of additives, including biocides, stabilizers and additives packages that increase lubricity, improve the Cetane number and provide detergents for keeping fuel systems clean.

And lastly, the fuel was regularly tested, maintained and, as necessary, polished through portable filters.

So, the answer to “how long does diesel fuel last” is “it varies.” But with proper fuel stability gained through sound storage and the use of diesel fuel treatments like Diesel STA-BIL® you can fight off fuel degradation for a relatively long period of time and keep costs low and controlled.

Hi Wayne, we recommend using it with every new tank of gas. It will keep your fuel fresh for up to 12 months. Please contact us at marketing@goldeagle.com if you have any questions about this. Thank you.

My diesel pickup, and therefore its fuel, sits for months at a time in between camping “roadtrips”. The longest period of sitting is about six months over most of the late fall to early spring. I am going to start using Sta-Bil Diesel Stabilizer at fill-ups but am wondering if I should also be using Sta-Bil 22283 Diesel Biocide also. I saw this product at my auto supple store but don’t see this product on your web-site and I don’t see if the Stabilizer accomplishes the biocide treatment.

Hi Scott, we stopped manufacturing this product. However, if you do still find it in-stores then yes it would work for your Diesel fuel to prevent microbial growth. Please contact us at marketing@goldeagle.com and let us know if you have any questions. Thank you.

What about diesel emergency generators? We have one that has had the same fuel in it for almost 17 years. We start it up once a month and it seems to run fine. It holds 1,000 gallons. How often and how much Sta-Bill for it?

Hi Erwin, Our STA-BIL Diesel has a treatment rate of 1 oz. (30mL) treats up to 10 gallons (38L) of fuel for in-season use. For storage: Use 1 oz. (30mL) to 5 gallons (19L). So, for a 1,000 gallon tank we would recommend 100 ounces of STA-BIL Diesel for in-season use and 200 ounces of STA-BIL diesel for storage. Please contact us at marketing@goldeagle.com if you have any questions about this. Thank you.

Hi Curly, First, make sure that this fuel is in good condition –especially if it was not treated with a stabilizer (bad smell is a good indicator). Check for excessive water/condensation –also known as phase separation (found at the bottom). Also, it would be a good idea to check for contamination such as fungi or “algae” (test kits are available). Add a diesel fuel system cleaner to the vehicle/equipment just to be on the safe side before running the truck’s engine. Please contact us at marketing@goldeagle.com if you have any questions about this. Thank you.

Hi, Francisco. At this point, before starting the engine, check under the hood and clean all debris –that includes dry leaves, animal nests and other contaminants. Check for broken or corroded components such as hoses and spark plugs (replace if necessary). Drain and replace all liquids ESPECIALLY the engine oil, coolant, transmission and brake fluid. The oil filter should also be changed. Drain the gas tank of any old fuel and replenish with fresh fuel. Lubricate the engine if necessary. Please let us know if you have any questions about this. Thank you.

Hello! Yes, you may mix STA-BIL® with other additives. However, we recommend to stick to the recommended dosage amount. Hope this helps and if you have any further questions please contact consumer support at producttechsupport@goldeagle.com

I have had Diesel in storage for 20 years for an Emergency Generator. When needed the generator is not performing as it did but still gets the job done. Am I to worry since after this long it may have settled to where it’s going to be. The fuel truck added 1/2 gallon of stabilizer when filled but nothing has been done since then. I have the tank higher on one end for water issues & the pick up at the high end. Probably 750 gallons left. What would you suggest, changing the fuel or testing, replacing or leave it alone. (The vendor claimed then, it was good for 10 years. They are out of business).

Hi, John. Typically, diesel fuel can last (under best conditions and quality of fuel) from 6-12 months. After that, it starts to oxidize, lose volatility, cetane, becomes stale, can develop microbial contamination and ultimately become solid (sludge). This can cause engine performance issues, jam fuel system parts (injectors, lines, filters etc.) and even cause overheating. If it has been that long, the best thing we could recommend is to drain and start fresh. At the very least you can have it tested.

Your advice about minimizing the water issue with diesel by keeping your tank full is really beneficial. Diesel fuel is super useful, and it may be a great idea to have it delivered to your location in order to avoid unnecessary trips. If I were to need such services, I would contact a fuel delivery company that works in a timely manner. http://www.fuelmanhawaii.net/services